Better batteries for electric cars

A slogan to sum up this year’s bill of auto shows might read “Hybrids! Electric cars! Fuel cells! You name it, we’ve got it! Or, will soon … really.” It’s hard to count how many times we’ve heard about breakthroughs in electric cars. Yet, so far, little has come of the hype.

Ask around and you may hear that electric cars are too expensive, they’re a threat to the combustion-engine industry, or the technology just isn’t there yet. But dig deeper and one reason holds fast for their delay: batteries. Ron Freund, chairman of the nonprofit Electric Auto Association, says that despite all the advances in electric cars, “We still need better batteries.”

The most recent advance came in December 2007, when Stanford University engineering and materials scientist Yi Cui increased tenfold the amount of energy a lithium-ion (also known as Li-ion) battery can store. By making the anode from silicon nanowires, Cui upped the capacity and durability of the electrode. “It’s a revolutionary development,” he says.

In fact, it would be a major breakthrough if the discovery could be applied to electric car batteries. We carry gasoline in a fuel tank; similarly, we need a portable container for hauling electrical energy. When it comes to electric cars, we have just a handful of options for rechargeable batteries. Some of the most popular are lead-acid and nickel batteries. But the latest newsmaker is Li-ion. Enthusiasm about the battery took off in 2002, when material scientist Yet-Ming Chiang and his MIT colleagues increased the conductivity of lithium iron phosphate, making it a better choice for use in battery electrodes. The technology is currently popular in cell phones and laptops because it packs a lot of energy into a small, lightweight cell. It can be recharged hundreds of times and holds its charge when idle.

Thanks to these qualities, companies from General Motors to Tesla are talking about eco concept cars powered by Li-ion batteries. Despite breakthroughs like Chiang’s and Cui’s, it may be years before they’re available for purchase. GM’s much touted hybrid plug-in Chevy Volt, for example, will run on this promising technology, but the Volt isn’t expected for sale until at least 2010.

An electric car battery has to be light, small, energy dense, and quick to recharge. But it also has to be relatively cheap, long lasting, and safe. Li-ion batteries received some bad press in 2006, when a few blew up after overheating in laptops. The explosions proved that what works in a lab may be far from ready to be mass-produced for cars.

“From the time a fundamental discovery is made and someone builds a test shell, it’s typically seven to ten years before it’s available as a product. That’s been repeated over and over,” says David Sivertsen, head of research and development for AC Propulsion, an electric car technology company.

“I remain skeptical of new battery breakthroughs,” says Martin Eberhard, the departed founder of Tesla Motors, but he concedes that he’s “intrigued” by Cui’s discovery. If it “increases energy density with the same lifespan, that alone would change the world.”

Story by Victoria Schlesinger. This article originally appeared in "Plenty" in May 2008.